Palm cooling for endurance sports
A reader sent me a link to Bex Runner’s “core cooling device” — essentially a small gel pack that you freeze and strap to your palms. So is it a useful device, or a stupid gimmick? Tough call.
There has actually been a fair amount of research on palm cooling over the last decade or so. I blogged last year about a study that found people lifting weights were able to lift more if they cooled their palms between sets. In that case, the palm-cooling device was a fancy one that also applied negative pressure to the palm to help prevent blood vessels from constricting with the cold. That ensures that lots of blood flows through the open vessels, past the cool palms, in order to better cool the rest of the body.
Still, the total cooling power of these devices is rather limited. Another study published last year compared the same palm cooling device to an Army cooling vest, and found that the palm cooling didn’t reduce heat strain during treadmill walking. They estimate that the vest was able to extract 55% of the heat generated during the trial, while palm cooling was only able to extract 14% of the heat.
The palm-cooling stuff is just one, small branch of the “ergogenic cooling” literature, and all sorts of theories have been proposed about how it does or doesn’t work. The crucial message that the weight-lifting study tells us, is that it doesn’t work by altering local muscle physiology. The chest muscles weren’t cooled, and yet the weight lifters lifted more weight. As the authors (from Robert Robergs’s group at the University of New Mexico) wrote:
[O]ur findings can only be explained by the central processing of peripheral input from afferent nerves and/or changes in core blood temperature and as such these results fit within the theory of the [Central Governor Model] of the regulation of fatigue and the final cognitive decision to end exercise.
If that’s the case, the palm-cooler doesn’t need to actually alter your physiology to make you run faster — it just needs to convince your brain that your body is in less distress than it would otherwise be. Does this particular Bex device do that in way that makes a practical difference to running performance in the heat? I have no idea — they need some independent studies to demonstrate it. But the mechanism is plausible.
(If it does work, there are still some questions. At a race, you’d have some logistical difficulties keeping it frozen until the start. For training, we get back to the question: is it really useful to use devices that make training easier? Or is that sort of self-defeating, because the whole point of training is to challenge yourself? If you run a tempo run in 30 minutes unaided, or 29 minutes with cooled palms at the same effort, do you actually get any superior benefit from the faster pace at the same effort? Or do you lose an opportunity to adapt to heat?
Training aside, I suppose if it enhances comfort on a hot day so that you can simply get your run in, that’s a plus.)